<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="js/jquery-3.2.1.js"></script>
</head>
<body>
    <div class="parent">
        <div class="one">one</div>
        <div class="two">two</div>
        <div class="three">three</div>
    </div>
    <script>
        let sibling = $(".two").siblings();
        console.log(sibling);

        let parent = $(".two").parent();
        console.log(parent);

        let first = $(".parent div").eq(0);
        console.log(first);

        let two = $(".parent").find(".two");
        console.log(two);

        let children =  $(".parent").children();
        console.log(children);

        let index = $(".parent div:last-child").index();
        console.log(index);
    </script>
</body>
</html>